Studies are continuing to compare the frequency of calcium salt crystalluria among normal subjects and patients who have formed calcium-containing kidney stones with respect to the composition of the urines without and with crystals. In addition, the relationship of the augmentation of urinary calcium concentration after glucose ingestion on the occurrence of calcium crystalluria is being examined. Studies of the mechanism by which carbohydrate ingestion inhibits net renal tubular reabsorption of calcium and magnesium is being examined by determining the interaction of the carbohydrate effect with other factors, such as volume expansion and various diuretics that are known to inhibit tubular cation reabsorption. Studies of the mechanism of basal hypercalciuria among stone formers as compared to normal subjects are in progress. Finally, studies of Vitamin D metabolism in man have been begun. The effects of metabolic acidosis, phosphate depletion, and of the anephric state in patients awaiting cadaveric renal transplantation are being evaluated.